1. Field of the Invention
The present invention generally relates to a data reproduction method and apparatus, and more particularly to a data reproduction method and apparatus for recovering data from a readout signal obtained from an optical storage medium to which the data is written at a high recording density.
2. Description of the Related Art
With recent developments of inexpensive, large-capacity magneto-optical disks with good reliability, the use of such media for recording and reproduction of pictures, image data, program codes and others is increasing in various fields.
There is the demand for magneto-optical disk drives that match with the requirements of large-capacity magneto-optical disks, and the disk drives require the ability to record data onto the medium at a high recording density and the ability to reproduce the data from the medium at a high density with good accuracy. A magnetic field modulation recording technique is known as a method of recording data onto the medium at a high recording density. Meanwhile, a magnetically induced super resolution (MSR) technique that utilizes an MSR medium is known as a method of reproducing data from the medium at a high density.
In a conventional partial response maximum likelihood (PRML) technique, the data reproduction that requires maximum likelihood estimation of a partial response with a large constraint length and a partial response with a small constraint length is carried out by making use of a single PRML system. In designing the PRML system, it is necessary that the PRML circuit match with the partial response having a larger constraint length. However, if such requirements are met, the size of the PRML circuit is increased in proportion to the constraint length of the partial response, and such PRML circuit is difficult to implement.